Glass flakes allow resin moldings to have improved strength and dimensional accuracy when being dispersed, for example, in a resin matrix. These glass flakes are mixed in coating materials as liners and are then applied to metal or concrete surfaces.
Glass flakes exhibit metallic colors when the surfaces thereof are coated with metal. On the other hand, they exhibit interference colors due to interference of reflected light when the surfaces thereof are coated with metal oxides. That is, a glass flake coated with a coating film formed of metal or metal oxide also can be used as a luster pigment.
Luster pigments produced with glass flakes as described above are commonly used for applications such as coating materials and cosmetics where color tone and luster are considered to be important.
JP 63 (1988)-201041 A describes, as suitable compositions for glass flakes, compositions of C glass produced with chemical durability being considered to be important, E glass developed for electronic products, and sheet glass.
JP 2001-213639 A describes glass flakes with excellent chemical durability. The glass flakes with excellent chemical durability contain neither diboron trioxide (B2O3) nor fluorine (F), which are volatile components, and the content of alkali metal oxides therein is 5 mass % or lower.
Glass compositions that are not flaky but fibrous with lower contents of alkali metal oxides are disclosed in the following publications:                JP 61 (1986)-14152A: “Glass Fiber”        JP 2001-515448 A: “Boron-Free Glass Fibers”        JP 2003-500330 A: “Glass Fiber Composition”        JP 2004-508265 A: “Glass Fiber Forming Compositions”        
Glass flakes can be produced by using an apparatus described, for example, in JP 5 (1993)-826 A. With the apparatus described in the publication, a molten glass base material is blown up into a balloon shape with a blow nozzle to form a hollow glass film, and this hollow glass film is crushed with a pressure roll. Thus glass flakes can be obtained.